Printing ink for use on flexible films

ABSTRACT

A low viscosity printing ink composition, based on acrylic terminated urethanes, is made which has a rapid curing rate and forms a cured impression that has a good adherence and flexibility. The ink can be used on flexible films, such as sausage casings, without cracking or bleeding.

RELATED APPLICATIONS

This application is a continuation-in-part of copending U.S. patentapplication Ser. No. 428,995, filed Sept. 30, 1982.

FIELD OF THE INVENTION

The present invention relates to a printing ink composition suitable forprinting on flexible polymeric films. More particularly, the presentinvention is directed to a printing ink composition for printing uponregenerated cellulosic films such as those used for sausage casings. Theinks of the invention can be rapidly cured to a tack-free state byexposure to ultraviolet light.

BACKGROUND OF THE INVENTION

A satisfactory ink for printing upon polymeric films, such asregenerated cellulose films used in sausage casings, should cure to forma tack-free printed impression with good adhesion and abrasionresistance, and, yet, the cured impression should be flexible such thatit will not crack upon flexing, wrinkling or stretching of the film. Asatisfactory ink should also have a rapid curing rate, since methods ofprocessing and handling sausage casings are quite rapid. Therefore, arapid curing rate of the ink is desirable to be compatible with thesehigh-speed handling and processing methods.

An example of such an ink for use upon such polymeric films is thatdisclosed in U.S. Pat. No. 3,316,189 to G. M. Adams. Disclosed is an inkcomposition, curable by the application of heat, that comprises a polyolprepolymer, such as polyester, polyether or castor polyols, anisocyanate prepolymer prepared from a polyisocyanate, a polymeric resinhardener, a pigment, and a volatile organic solvent.

With this ink, as with a number of other heat curable inks, the presenceof the volatile organic solvent is undesirable, because, upon curing ofthe ink, this solvent volatilizes into the atmosphere creating possiblehealth and safety problems. Efforts have been made to solve this problemby reducing or even eliminating the volatile solvents. A problemassociated with this approach, however, is an increase in viscosity ofthe composition causing difficulties in handling and application. It is,therefore, desirable to produce a composition of proper viscosity thatis free of volatile solvents. It is also desirable that the compositionbe curable using a minimal amount of energy.

Ink compositions have been developed that are free of volatile solvents,are curable with a low amount of energy by ultraviolet light, and have alow viscosity. However these compositions, being directed mainly toprinting on paper or metal substrates have generally not been entirelysuitable for use with flexible polymeric films such as those used forsausage casings. Although many of these compositions cure rapidly andare suitable for high-speed processing requirements, the printedimpression formed by the cured ink is often brittle and is subject tocracking when the casing is folded or stretched. Other ultraviolet lightcurable ink compositions show greater flexibility and will cure to formimpressions that will not crack. However. these compositions generallyhave unsuitably slow curing rates and/or form tacky impressions withpoor adhesion to the polymeric film substrate. Polymeric films, such asthe cellulosic type used in food packaging require that the impressionbe flexible, and have good adhesion. The impression must be fully curedand not be tacky or rub off. It is generally the case that an inkcomposition that cures more rapidly and forms nontacky impressions ofgreater adherence is often more brittle and less flexible.

Thus, an ink composition having the conflicting and often exclusiveproperties of rapid cure under ultraviolet light and formation of animpression having physical properties suitable for use with flexiblefilms, such as sausage casings, would be highly desirable. To form suchan ink is very difficult, because of the many unpredictable factorsassociated with ink manufacture. The components of the ink will ofteninteract in an unpredictable manner to adversely affect the propertiesof the ink such as, for example, the cure rate, and/or the physicalproperties relating to handling of the ink, such as viscosity and shelflife.

It is, therefore, an object of the invention to provide an ultravioletcurable ink composition that possesses the combination of properties tomake it suitable for use for printing on flexible films.

SUMMARY OF THE lNVENTION

It has now been found that an ink composition can be made that is freeof volatile solvents, is rapidly curable with ultraviolet light, andforms an impression oF suitable physical properties for use on flexiblepolymeric films such as sausage casings.

The invention in one aspect is an uItraviolet light curable inkcomposition which comprises

(i) a first urethane comprising a polyol urethane which is the reactionproduct of about one equivalent of an isocyanate containingintermediate, the isocyanate intermediate being the reaction product ofabout one equivalent of a monomeric polyol and about two equivalents ofan organic polyisocyanate, and one about equivalent of a monomericolefinically unsaturated compound containing exactly one activehydrogen, and

(ii) a second urethane comprising an acrylate-capped polycaprolactonedefined by the formula; ##STR1## where Z is hydrogen or methyl; Q is theresidue remaining after reaction of the caprolactone polyol with theisocyanato and acrylyl compound, hereinafter more fully described; R isa linear or branched divalent alkylene having from about 2 to about 5carbon atoms; G is the polyvalent residue remaining after reaction of asubstituted or unsubstituted polyisocyanate with the caprolactone polyoland acrylyl compound and can be a linear or branched alkylene havingfrom 1 to about 10 carbon atoms, or arylene, alkarylene and aralkylenehaving from about 6 to about 12 carbon atoms, cycoalkylene having fromabout 5 to about 10 carbon atoms, or bicycloalkylene having from about 7to about 15 carbon atoms; and x is an integer having a value from 1 to4;

(iii) an ultraviolet photoinitiator in an amount sufficient to cure theink composition when exposed to ultraviolet light, and

(iv) a pigment; with the proviso that the first urethane and the secondurethane are present in an amount such that the weight ratio of thefirst urethane to the second urethane is from about 2:5 to about 3:2,preferably about 3:5 to about 5:5.

Another aspect of the invention is an ultraviolet curable ink comprisinga first urethane which comprises the reaction product of an acrylatedepoxidized drying oil and an organic isocyanate; a second urethane asdefined above, an ultraviolet photo-initiator, and a pigment such thatthe first urethane and the second urethane are present in the weightratios described above.

It is preferable to add a reactive diluent monomer, more fully describedbelow, to provide a suitable viscosity for use as an ink.

The combined amounts of the first urethane and the second urethaneshould preferably be about from about 20 weight percent to about 80weight percent, most preferably about 50 weight percent to about 70weight percent. The reactive diluent monomer, if used, should be presentin an amount from about 2 weight percent to about 30 weight percent,preferably about 5 to about 20 weight percent. The ultravioletphotoinitiator should be present in an amount from about 1 weightpercent to about 10 weight percent, preferably about 3 weight percent toabout 7 weight percent. The pigment should be present in an amountgreater than 0 weight percent up to about 70 weight percent, preferablyabout 10 weight percent to about 50 weight percent. The above weightpercentages are based upon the total weight of the ink composition.

The active hydrogen atoms referred to herein are those which displayactivity according to the Zerewitinoff test as described by Kohler, J.Am. Chem. Soc. 49, 3181 (1927).

DESCRIPTION OF THE INVENTION POLYOL URETHANE

The polyol urethanes used in the invention are made by reacting aboutone equivalent of a monomeric polyol and an equivalent of an organicpolyisocyanate, preferably a diisocyanate, to form an intermediatecompound with terminal isocyanate groups. The intermediate compound isthen reacted with an equivalent of an olefinic unsaturated compoundhaving at least one active hydrogen. These compounds and a process formaking the same are disclosed in U.S. Pat. No. 4,174,307, issued Nov.13, 1979 to W. Rowe.

The monomeric polyols useful for making the polyol urethane for use inthe invention are monomeric diols. triols, tetraols, and the like.Illustrative of the monomeric diols are ethylene glycol, propyleneglycol, 1,3-butylene glycol, 1,4-butane diol, 1,5-pentanediol,hexamethylene glycol, etc., mono fatty acid esters of trimethylolethane,trimethylolpropane, and the like. Illustrative of the monomeric triolsare trimethylolpropane, glycerol, castor oil, fatty acid monoglyceridessuch as ricinoleic monoglyceride, ricinoleic monoglycolate, monofattyacid esters of pentaerythritol, etc. Illustrative of the tetraols ispentaerythritol. Preferably, the polyols have a molecular weight of upto about 1,000 or higher. More preferably. they have a molecular weightof up to about 950, and most preferably, up to about 500.

Illustrative of the organic diisocyanates for use in making the polyolurethane useful in the invention are, for example, the aromatic,aliphatic, and cycloaliphatic diisocyanates, and combinations thereof.These include 2,4-tolulene diisocyanate, m-phenylene diisocyanate,xylylene diisocyanate, 4-chloro-1,3-phenylene diisocyanate,4,4'-biphenylene diisocyanate, 1,4-cyclohexylene diisocyanate,1,5-tetrahydronaphthalene diisocyanate, methylene dicyclohexylenediisocyanate and the like. Diisocyanates in which each of the twoisocyanate groups is directly attached to a ring are preferred, since,generally, they react more rapidly with polyols. Especially preferredtypes are ##STR2## The diisocyanates can contain other substitutents,although those which are free from reactive groups, other than the twoisocyanate groups, are preferred.

The above described polyols and organic diisocyanates are reacted toform an intermediate which is then reacted with an olefinicallyunsaturated compound to form the polyol urethane useful in theinvention. Illustrative of these olefinically unsaturated compounds arethose which contain at least one active hydrogen atom and at least oneaddition polymerizable olefinically unsaturated grouping, such as C=C .Those compounds containing one of each of these groups is preferred.Specifically illustrative of such monomeric unsaturated compounds arethose containing active hydrogen atoms in a group such as aliphatichydroxyl, phenolic hydroxyl, thiol, carboxyl, amine or amide and anunsaturated grouping, preferably present as terminal unsaturation suchas, for example the vinyl and acrylic compounds. Preferably,olefinically unsaturated compounds contain from about 3 to about 12carbon atoms. Examples thereof are acrylic acid, cinnamic acid,methacrylic acid, hydroxyalkyl acrylates and methacrylates such ashydroxyethyl acrylate and methacrylate, cinnamyl alcohol, allyl alcohol,diacetone acrylamide, unsaturated compounds containing secondary aminoor amido groups, and the like.

A procedure that may be used to make the polyol urethane useful in theinvention comprises placing about 2 equivalents of the organicpolyisocyanate in a reaction vessel for each equivalent of activehydrogen atoms in the monomeric polyol. Preferably, the polyisocyanateis a diisocyanate. The polyol and the polyisocyanate should bewater-free. The polyisocyanate may be reacted under an inert gasatmosphere such as, for example, nitrogen, with the polyol attemperatures of from about room temperature to about 70° C. Elevatedtemperatures are preferred. The polyol must be added slowly, e.g.,incrementally, with stirring or agitation to the diisocyanate which ismaintained at the reaction temperature, typically about 65°±5° C., bythe rate of addition of the polyol and/or by heating and/or cooling,depending on the exotherm developed. The reaction temperature is helduntil the theoretical free remaining isocyanate weight percent isobtained as determined by titration of an aliquot from the reactionvessel with dibutylamine.

When the reaction is theoretically complete, the temperature ismaintained and there is added with agitation one equivalent of themonomeric olefinically unsaturated compound and an effective amount of avinyl polymerization inhibitor, such as hydroquinone. An effectiveamount of a catalyst is added to increase the speed of the reaction.Illustrative of the catalysts that may be used are metallic catalystssuch as the organo metallics. These include the organotin compounds,such as stannous octoate, dibutyl tin dilaurate, etc.; organo-cobaltcompounds such as cobalt naphthenate; lead compounds such as leadoctoate; and zinc compounds such as zinc octoate. Other known catalystssuch as mineral acids, such as hydrochloric acid, nitric acid or thelike, or phosphines can be used. The reaction is continued for a periodof time to assure complete reaction, which is when there are essentiallyno remaining isocyanate groups. The reaction mixture is cooled andyields the polyol urethane useful in the invention.

ACRYLATED EPOXIDIZED DRYING-OIL URETHANE

The acrylated epoxidized drying-oil urethane derivatives useful in theinvention are produced by the reaction of an organic mono orpoly-isocyanate with an acrylated epoxidized drying-oil compound.

Acrylated epoxidized drying-oil urethanes are derived from acrylatedepoxidized drying oil compounds. A description of the acrylatedepoxidized drying-oil compounds and methods for the production of sameare disclosed in U.S. Pat. No. 3,125,592 issued Mar. 17, 1964 to Nevin,and U.S. Pat. No. 3,450,631 issued June 17, 1969 to Steinberg. The abovepatents disclose the use of soybean oil in the making of the acrylateddrying-oil compounds and the urethane derivatives thereof. Although notdisclosed in the above patents, linseed oil may also be used to makeacrylated drying-oil compounds and urethane derivatives thereof bydirectly substituting linseed oil for soybean oil in the processes formaking same. Thus, the term "drying-oil" as used herein means soybeanoil and linseed oil.

The acrylated epoxidized drying oil compound is formed by reactingepoxidized drying-oil with an acrylic compound.

A class of these compounds is described in U.S. Pat. No. 4,025,477,issued to Borden et al. on May 24, 1977. Therein is described compoundswhich are the reaction product of an epoxidized drying oil and acrylicor methacrylic acid. This reaction, described in U.S. Pat. No.4,025,477, proceeds with the opening of the epoxide ring in the moleculeand the addition of the acid. This can be represented by the equation:##STR3## where X is hydrogen or methyl. The acrylated epoxidizeddrying-oil compound contains an average of at least two such acrylyl ormethacrylyl groups per molecule and, in addition, it may also containsome unreacted oxirane, preferably less than 2 weight percent unreactedoxirane.

Another class of acrylated epoxidized drying oils useful for making theepoxidized drying oil urethanes of the invention are the reactionproduct of an epoxidized drying oil and pentaerythritrol acrylate.

The acrylated epoxidized drying oil compound is reacted with anisocyanate to form the acrylated epoxidized drying-oil urethanederivative useful in the invention. Among the isocyanates that can beused in producing these derivatives are those represented by the generalformula, R(NCO), wherein R can be an alkyl group of from 1 to about 15carbon atoms, or a substituted or unsubstituted aryl group having from 6to about 12 carbon atoms, and n can be an integer greater than 1,preferably 1 to 4, most preferably 1 or 2. lllustrative thereof, one canmention methyl isocyanate, ethyl isocyanate, butyl isocyanate,2-ethylhexyl isocyanate, chloroethyl isocyanate, cyclohexyl isocyanate,phenylisocyanate, p.chlorophenyl isocyanate, benzyl isocyanate, naphthylisocyanate, o-ethylphenyl isocyanate, 2,4-tolylene diisocyanate,2,6-tolylene diisocyanate, cyanate, 4,4'-diphenylmethane diisocyanate,polymethylene polyphenylisocyanate, dianisidine diisocyanate, 1,6-hexanediisocyanate, m-xylylene diisocyanatne, dicyclohexyl-4,4'-methanediisocyanate, cyclohexane-1,4-diisocyanate, 1,5-naphthalenediisocyanate,1-isocyanato-3-isocyanatomethyl-3,3,5-tri-methylcyclohexane,diphenylene-4,4-diisocyanate, bicyclo[2.2.1]hept-2-en-5-isocyanate. andthe like. Any of the known organic isocyanates can be used, includingthe tri-and tetra-isocyanate compounds. All of these are well known tothose skilled in the art.

The reaction of the acrylated epoxidized drying oil compound with theisocyanato group is via a hydroxyl group to form a urethane link. If theacrylated epoxidized drying oil was derived from acrylic or methacrylicacid, as described in U.S. Pat. No. 4,025,473, the urethane derivativesof the acrylated epoxidized drying oil compound contain the group:##STR4## where X is hydrogen or methyl. The number of such groupspresent can be controlled by the amount of isocyanate compound added tothe reaction. All of the hydroxyl groups in the acrylated epoxidizeddrying-oil compound can be reacted with an isocyanato group, or lessthan all can be so reacted. Thus, from about 2 to about 100 percent ofthe available hydroxyl groups can be converted to urethane groups;preferably from about 50 to about 90 percent thereof are reacted withthe isocyanato group and converted to the urethane group.

The reaction between the acrylated epoxidized drying oil compounds andthe isocyanate to form the acrylated epoxidized drying-oil urethanesuseful in the invention can typically be carried out by the slowaddition of the isocyanate to the acrylated epoxidized drying-oilcompound. The order of addition, however, is not critical. Thetemperature can be from about 10° C. to about 100° C., preferably fromabout 20° C. to about 80° C., and most preferably from about 40° C. toabout 60° C. After the addition has been completed, the reaction mixtureis stirred to ensure completion of reaction. The time required willvary, of course, depending upon the size of the batch, the reactantsused, the temperature of the reaction and other variables known toaffect chemical reactions in general. A solvent can be present ifdesired. It is preferably an inert solvent that will not interfere withthe reaction. These are well known and include ethers, hydrocarbons,ketones and esters. Examples are diethyl ether, p-dioxane, dibutylether, tetrahydrofuran, diisopropyl ether, methyl ethyl ketone, methyln-propyl ketone, methyl propionate, ethyl acetate, hexane. toluene,xylene, benzene, and the like. Of course, the presence of water is knownto be detrimental when an isocyanate group is involved since this groupreacts readily and rapidly with water. Any one of the conventionalcatalysts known to promote the reaction of an isocyanato group with areactive hydrogen atom of the hydroxyl group can be used. The number ofsuch catalysts is large, and illustrative thereof one can mentiontriethylamine, N,N,N',N'-tetramethylbutane-1,3-diamine, dibutyltindilaurate, stannous octoate, stannous laurate, dioctyltin diacetate,lead octoate, bis[2-(N,N-dimethylamino)ethyl]ether,1,4-diazabicyclo[2.2.2]octane and the like.

ACRYLATE-CAPPED POLYCAPROLACTONES

The acrylate-capped polycaprolactones useful in the invention aredescribed in U.S. Pat. No. 3,700,643, issued Oct. 24, 1972 to Smith etal. They are reaction products of a caprolactone polyol, a substitutedor unsubstituted isocyanate, and an acrylyl compound, and can be definedby the formula; ##STR5## where Z is hydrogen or methyl; Q is the residueremaining after reaction of the caprolactone polyol with the isocyanateand acrylyl compound, hereinafter more fully described; R is a linear orbranched divalent alkylene having from 2 to about 5 carbon atoms; G isthe polyvalent residue remaining after reaction of the polyisocyanatewith the caprolactone polyol and acrylyl compound and can be a linear orbranched alkylene having from 1 to about 10 carbon atoms, or arylene,alkarylene and aralkylene having from 6 to about 12 carbon atoms,cycloalkylene having from 5 to about 10 carbon atoms, or bicycloalkylenehaving from 7 to about 15 carbon atoms; and x is an integer having avalue from 1 to 4, preferably 2. Preferably R is linear having 2 or 3carbon atoms.

The polycaprolactone polyol residue represented by Q is produced fromcaprolactone or a caprolactone polyol. The caprolactone polyols, whethermonohydric or polyhydric, are commercially known compositions of matterand are fully described in U.S. Pat. No. 3,169,945 issued Feb. 16, 1965to Hostettler and Young. As used in this specification, the termscaprolactone polyols and polycaprolactone polyols include compoundshaving one or more hydroxyl groups. As described therein, thecaprolactone polyols are produced by the catalytic polymerization of anexcess of the caprolactone compound with an organic functional initiatorhaving at least one reactive hydrogen atom: the polyols can be singlecompounds or mixtures of compounds, either can be used in thisinvention. The method for producing the caprolactone polyols is of noconsequence. The organic functional initiators can be any hydroxylcompound, as shown in U.S. Pat. No. 3,169,945, and include methanol,ethanol, propanol, decanol, benzyl alcohol, and the like: diols such asethylene glycol, diethylene glycol, triethylene glycol, 1,2-propyleneglycol, dipropylene glycol, 1,3-propylene glycol, polyethylene glycol,polypropylene glycol, poly(oxyethylene-oxypropylene) glycols and similarpolyalkylene glycols, either block, capped or heteric, containing up toabout 40 or more alkyleneoxy units in the molecule,3-methyl-1,5-pentanediol, cyclohexanediol,4,4'-methylene-biscyclohexanol, 4,4'-isopropylidenebiscyclohexanol,xylenediol, 2-(4-hydroxymethylphenyl)-ethanol, and the like; triols suchas glycerol, trimethylolpropane, 1,4 -butanediol, 1,2,6-hexanetriol,triethanolamine, triisopropanolamine, and the like; tetrols such aserythritrol, pentaerythritol. N,N,N',N'-tetrabis(2- hydroxyethyl)ethylenediamine, and the like.

When the organic functional initiator is reacted with the caprolactone areaction occurs that can be represented in its simplest form by theequation: ##STR6## In this equation the organic functional initiator isthe R"(OH)_(x) compound and the caprolactone is the ##STR7## compound;this can be preferably caprolactone itself or a substituted caprolactonewherein R' is an alkyl, alkoxy, aryl, cycloalkyl, alkaryl or aralkylgroup having up to twelve carbon atoms and wherein at least six,preferably all, of the R' groups are hydrogen atoms. Thepolycaprolactone polyols that are used to produce the acrylate-cappedpolycaprolactone polyols of this invention are shown by the formula onthe right hand side of the equation; they can have a molecular weight offrom 130 to about 20,000. The preferred caprolactone polyol compoundsare those having a molecular weight of from about 175 to about 2,000.The most referred are the polycaprolactone diol compounds having amolecular weight of from about 350 to about 1,000; these are mostpreferred because of their low viscosity properties. In the formula, mis an integer representing the average number of repeating units neededto produce the compound having said molecular weights.

G is the residue of a polyisocyanate. Suitable polyisocyanates for usein forming the caprolactone urethanes include 2,4-tolylene diisocyanate,2,6-tolylene diisocyanate, 4.4'-diphenylmethane diisocyanate,dianisidine diisocyanate, tolidine diisocyanate, hexamethylenediisocyanate, the m- and p-xylene diisocyanates, tetramethylenediisocyanate, dicyclohexyl-4,4'-methane diisocyanate,cyclohexane-1,4-diisocyanate, isophorone diisocyanate, 1,5-naphthylenediisocyanate, 4,4'-diisocyanate di- phenyl ether, 2,4,6-triisocyanatetoluene. 4,4',4"-triisocyanate triphenyl methane, di-phenylene-4,4-diisocyanate, the polymethylene poly- phenylisocyanates,as well as any of the other organic polyisocyanates known in the art.

Illustrative of R, one can mention the divalent radicals ethylene,1,3-propylene, 1,2-propylene, butylene, pentylene, and the like.Suitable alkyl groups, dependent on the chain length definition setforth, are methyl, ethyl, propyl, isopropyl, butyl, isobutyl, pentyl,neopentyl, hexyl, octyl, 2-ethyloctyl, decyl, dodecyl, and the like.These are all obvious and known to those skilled in the art.

The acrylyl compounds suitable for use in producing the acrylate-cappedpolycaprolactones are the hydroxyalkyl acrylates and the hydroxyalkylmethacrylates of the formula ##STR8## wherein Z and R are as previouslydefined. The hydroxyalkyl acrylyl compounds are well known and can beillustrated by hydroxyethyl acrylate, hydroxyethyl methacrylate,hydroxypropyl acrylate, hydroxypentyl methacrylate, and the like.

The acrylate-capped polycaprolactone polyol derivatives can be producedby several procedures and can be single compounds or mixtures ofcompounds.

The acrylate-capped polycaprolactone urethanes useful in the inventioncan be produced by heating a mixture of polycaprolactone polyol,hydroxyalkyl acrylate and organic isocyanate, preferably in contact withone of the known catalysts for urethane reactions. They includetriethylene diamine, morpholine, N-ethylamine. piperazine,triethanolamine, triethylamine, N,N,N',N'-tetramethylbutane-1,3-diaminedibutyltin, dilaurate, stannous octoate, stannous laurate, dioctyltindiacetate, lead octoate, stannous oleate, stannous tallate, dibutyltinoxide, etc. The reaction can also be carried out by adding the organicisocyanate to a mixture of the other components, or by feeding thepolycaprolactone polyol and hydroxyalkyl acrylate, either as a mixtureor in separate streams to the organic isocyanate. In any event, thereaction can be carried out either in the presence or absence of asolvent. The solvent is preferably one which does not contain activehydrogen groups, i.e., hydroxyl, amino, amido, etc., in the solventmolecule. Among the suitable solvents one can mention the hydrocarbonssuch as octane, benzene, toluene, the xylenes, etc.; the ketones such asacetone, methyl ethyl ketone, etc.; the ethers such as diisopropylether, di-n-butyl ether, etc.; and the reactive solvents or reactiondiluent monomers, described below, normally used in producing coatingcompositions that subsequently become incorporated in the ink.

The mole ratio of the polycaprolactone polyol to hydroxyalkyl acrylatecan range from 1:0 to 1:25 preferably from 1:2 to 1:5 with sufficientorganic isocyanate being added to react with all or substantially all ofthe hydroxyl groups present.

The reaction temperatures can vary from about 20° C. to about 90° C. orhigher, but are preferably from about 50° C. to about 75° C. Thereaction time will vary according to the size of the batch, the natureof the organic isocyanate, polycaprolactone polyol and acrylyl compound,as well as the reaction temperature employed.

The reaction can be carried out in air or in an inert gas atmosphere.Precautions should be taken to exclude water, which is known to reactwith the isocyanate group. To prevent premature reaction of theunsaturated acrylyl group, about 5 to 1,000 ppm of a compound known toinhibit free radical polymerization can be added. These inhibitors arewell known and include phenothiazine, hydroquinone, the monomethyl etherof hydroquinone, 2,6-di-t-butyl-p-cresol and other hindered phenols.

Illustrative of polycaprolactone polyols that can be used as startingmaterials in the acrylate-capped polycaprolactones useful in theinvention one can mention the reaction products of a polyhydroxylcompound having from 1 to 4 hydroxyl groups with caprolactone. Themanner in which these caprolactone polyol compositions are produced isshown in U.S. Pat. No. 3,169,945 and many such compositions arecommercially available.

ULTRAVIOLET PHOTOINITIATOR

The photoinitiator is presented to absorb the ultraviolet radiation andinitiate the polymerization and cross-linking reactions that constitutethe curing of the ink composition. These photoinitiators are well knownin the art of ultraviolet light curable coatings and any photoinitiatoris suitable that provides for a sufficiently rapid cure rate.

Suitable photoinitiators include tetramethyldiaminobenzophenone(Michler's Ketone) in solution with benzophenone. Typically a solutioncomprising about 20 weight percent Michler's Ketone and 80 weightpercent benzophenone is used. Other suitable photoinitiators includeisobutyl bensin ether, diethoxy acetophenone, benzoin isopropyl ether,benzoin methyl ether and 2,2-dimethoxy-2-phenylacetophenone. Thepreferred photoinitiator is 2,2-dimethoxy-2-phenylacetophenone.

Preferably, the photoinitiator should be chosen such that the inkcomposition is stable at storage conditions (about 20°-30° C.). In thiscontext, "stable" means that there is no gelling or undesirable increasein viscosity over the time the ink composition is stored or there is nosignificant discoloration of the ink composition, such that the utilityof the composition of the ink is affected. Photoinitiators used whereinthe ink compositions did not gel within 26 days are2,2-dimethoxy-2-phenylacetophenone, and diethoxy acetophenone. Isobutylbenzoin ether and benzoin methyl ether caused gellation of the inkcomposition in 1 or 2 days.

The photoinitiator is preferably present in an amount of about 1 toabout 10 weight percent, most preferably about 3 weight percent to about7 weight percent, based on the total weight of the composition.

PIGMENT

Suitable pigments include colored organic and inorganic compounds ofdyes that are normally used to impart color. The pigment should besubstantially nonreactive with the components of the ink. Preferably thepigment should have a low absorption in the near ultraviolet lightspectrum. Suitable pigments are identified in Table A below.

                  TABLE A                                                         ______________________________________                                        Pigment             Pigment No.                                                                              Index No.                                      ______________________________________                                        Titanium Dioxide (Rutile)                                                                         White 6    77891                                          G.S. Benzidine Yellow (AAOA)                                                                      Yellow 17  21105                                          R.S. Benzidine Yellow (HR)                                                                        Yellow 83  --                                             Benzidine Orange (G)                                                                              Orange 13  21100                                          Naphthol Red        Red 170    --                                             Red Lake C          Red 53     15585                                          Carmine Red         Red 176    --                                             Watchung Red 2B     Red 48     15865                                          Quinacridone Red    Red 122    46500                                          Lithol Rubine       Red 57     15850                                          Phthalocyanine Blue Blue 15    74160                                          Carbazole           Violet 23  51318                                          Phthalocyanine Green                                                                              Green 7    74260                                          Carbon Black        Black 7    77266                                          Aluminum Flake      Metal 1    77000                                          ______________________________________                                    

The pigment should be used in an amount such that an impression isformed with good covering properties and a proper color density. Thepigment should not be used in such an amount that the ink will chalk ondrying or change the viscosity of the ink to an unacceptably high level.above about 65,000 centipoise at 25° C. Preferably the pigment is usedin an amount greater than 0 up to about 70 weight percent, mostpreferably about 10 to about 50 weight percent, based on the totalweight of the ink composition.

REACTIVE DILUENT MONOMER

The reactive diluent monomer in the composition of the invention isoptionally added to obtain a practical viscosity of the composition.Typically the viscosity should be from about 50 to about 65,000centipoise, preferably about 2,000 to about 20,000 centipoise, at 25° C.The reactive diluent monomer should be reactive, under the conditions inwhich the ink is cured, with the first urethane and the second urethanecomponents of the composition of the invention to form a crosslinkedresinous structure when the ink is cured. Since the preferred use of theink of the invention is for printing upon a food packaging, the reactivediluent monomer should preferably not impart an odor or a toxicity tothe cured ink. Suitable reactive diluent monomers are well known in theart. The preferred reactive diluent monomers are glycidyl methacrylateand H-vinyl-1-pyrrolidone. The reactive diluent monomer is preferablypresent in an amount of about 2 to about 30 weight percent, mostpreferably about 5 weight percent to about 20 weight percent, based onthe total weight of the ink.

The ink composition of the invention is made by mixing the components bymethods well known in the art. For example by use of a change-can mixer,dough mixer, sigma arm mixer, or the like. The ink is typically groundafter mixing, using, for example, a roll mill commonly used in inkmanufacture.

The ink composition is applied to a substrate by any suitable methodknown in the art such as offset printing, letter press, reverse roll,wire wound rod, air knife, flexography, gravure, or the like.

Although any substrate is suitable, the ink composition, as discussedabove, is designed for use on polymeric film substrates such as thoseused as sausage casings. These include substrates of regeneratedcellulose, fibrous-reinforced regenerated cellulose, treatedpolyethylene, polyethylene terephthalate, vinyl chloride-vinylidenechloride copolymer. polyvinylidene chloride, polyvinyl, polyvinylbutyral, polymethylmethacrylate, polystyrene acrylonitrile, celluloseacetate, glassine, ethylene vinyl acetate copolymer and the like. Thepreferred substrate materials are films of fresh and aged regeneratedcellulose, fibrous-reinforced regenerated cellulose and these same filmswith any of the various coatings common in the art. An example of such acoated film is the so-called "MP fibrous casing", which has a barrierlayer of polyvinylidene chloride resin.

The excellent adhesion properties of the cured ink impression of theinvention to the substrate, is best realized on film substrates coatedwith polyvinylidene chloride. For use on cellulosic substrates that arenot so coated, a coating of an uncured "primer" coating is preferred toincrease the adhesion of the ultra-violet radiation cured ink. Suitableprimers include resins based on polyester, vinyl. cellulose acetatebutyrate or acrylic ester, in a suitable solvent with polyfunctionalaromatic or aliphatic isocyanates. Examples of suitable resins include"Acryloid B-48"™ from Rohm & Haas Company, Philadelphia, Penna., whichis a solution of acrylate or methacrylate ester polymers, and "SaranF-120"™ from Dow Chemical Co., Midland, Michigan, which is a copolymerof vinylidene chloride and acrylonitrile. Suitable polyisocyanatesinclude those polyisocyanates commonly used in the art in the coatingtechnology, such as "Mondur CB-75"™, which is a polyisocyanate availablefrom Mobay Chemical Corporation, Pittsburgh, Pennsylvania. The primercoating can be applied as a solution of the primer coat material with anappropriate solvent in an amount to wet the substrate surface. Suitablesolvents include toluene, xylene, methylethylketone, nitropropane,CELLOSOLVE™ acetate (B-ethoxy-ethylacetate), and ethylacetate.Preferably, a primer coating should be chosen so as not to inhibit thesmoke permeability or other desirable physical properties of thesubstrate in relation to its use. An example of a suitable prime coatsolution is one comprising about 19 weight percent "Acryloid B-48"™, 77weight percent ethyl acetate and 4 weight percent "Mondur CB-75™".

The ink composition may also contain other additives commonly used inpolymerizable ink formulations. These include pigment dispersing agents,leveling agents, fillers, and polymerization inhibitors.

After application upon a substrate. the ink composition of the inventionis cured by exposure to ultraviolet light for a sufficient length oftime to cure the ink to a tack-free state. It is important that the inkbe fully cured to a tack free state to obtain the desired adhesionnecessary for sausage casing applications. Methods for curing inks withultraviolet light are well known in the art. When used upon sausagecasings, the ink composition of the invention can be cured rapidlyduring the normal processing of the casing, using a suitable in-lineultraviolet light curing apparatus. This eliminates the need foroff-line ink curing racks and the accompanying extra time and handlingrequired. These measures are generally necessary when usingsolvent-based conventional inks of the prior art that require asignificantly longer cure time.

The following examples illustrate the invention and are not intended tolimit it in any way.

In the following examples the compositions identified below were used;

Polyol urethane A (PU-A): The exact nature of this composition is notknown, but it is believed to have been made by the process ofabove-cited U.S. Pat. No. 4,174,307 by reacting a diisocyanate with apolyol to form an intermediate and reacting this intermediate with amonomeric olefinically unsaturated compound to form a polyol urethane.It was available from Polychrome Corporation, Yonkers, New York underthe tradename "UVIMER DV-588™".

Polyol urethane B (PU-B): The exact nature of this composition is notknown, but it is believed to have been made by the process ofabove-cited U.S. Pat. No. 4,174,307 by reacting a diisocyanate with apolyol to form an intermediate and reacting this intermediate with amonomeric olefinically unsaturated compound to form a polyol urethane.It was available from Polychrome Corporation, Yonkers, New York underthe tradenames "UVIMER DV-545™".

Acrylated Epoxidized Drying-Oil urethane A (AEDOU-A): This compositionwas made by reacting soybean oil with pentaerythritrol acrylate to forman intermediate. Pentaerythritrol acrylate is a mixture of mono-, di-,tri-, and tetraacrylates of pentaerythritrol, with an averagefunctionality of 3.1 to 3.3. The intermediate is reacted with anisocyanate to form acrylated epoxidized drying-oil urethane, which wasavailable from Union Carbide Corporation, Danbury, Connecticut under thetradename "Actomer X-80™".

Acrylate-capped polycaprolactone urethane A (APU-A): This compositionwas made essentially as described in the above cited U.S. Pat.No.3,760,643 by charging 569 g of isophorone diisocyanate and 1.68 g ofdibutyl tin dilaurate to a flask, equipped with a stirrer, thermometer,dropping funnel and reflux condenser, heated to 45° to 50° C., 530 g ofa difuntional polycaprolactone polyol with a molecular weight betweenabout 500 and 600 were added dropwise. 576 g of hydroxyethyl acrylatewere then added and the reaction continued until it was completed. Thepolycaprolactone polyol was available from Union Carbide Corporation,Danbury. CT, under the name "PCP-200™". Alternately, the inks of theinvention may also be made by using an acrylate-capped polycaprolactonemade essentially as described, except a caprolactone polyol availablefrom Union Carbide Corporation under the name "PCP-240™" is used insteadof "PCP-200™" and tetramethylene diisocyanate instead of isophononediisocyanate. "PCP-240™" is similar to "PCP-200™" but has a molecularweight of about 2000.

Acrylate-capped polycaprolactone urethane B (APU-B): This compositionwas made essentially as APU-A above.

Acrylate-capped polycaprolactone urethane C (APU-C): The exact nature ofthis composition is not known. It is believed to be made as described inthe above-cited U.S. Pat. No. 3,760,643. It was obtained from DeSoto,Inc., Des Plaines, Illinois under the tradename "DeSolite 2353-144™".

Unless otherwise indicated, the inks in the following examples were madeusing a three roller mill like those commonly used in ink manufacture.The ink components were thoroughly blended and ground in the mill untilthe components of the ink were finely ground and dispersed.

Unless otherwise indicated, the inks were applied to the subtrate byrolling a suitable quantity thereof on a glass plate and transferringthe applied ink from the glass plate to the substrate using a hand-heldrubber roller. An amount of ink was chosen such that an ink film ofabout 3 mils (0.08 mm) thick was produced.

The inks were cured with ultraviolet light using a Linde PhotocureSystem (PSCU), available from Union Carbide, Danbury, Connecticut, and amedium pressure mercury arc unit (MPHG). The PSCU contained 29 one-wattper inch cool mercury resonance lamps with a 46% UV output conversionefficiency. The lamps emitted short wave ultra-violet light atwavelengths of 1849 Angstroms and 2537 Angstroms, as well as visibleradiation. The air within the PSCU was inerted by replacing the air withan inert gas (nitrogen) to prevent oxygen from inhibiting surface cure.The MPHG was equipped with lamps emitting a range of ultravioletradiation with a wave length less than about 4000 Angstroms, as well asvisible and infrared radiation. To cure the ink, the substrate with theink thereon was passed through the PSCU then through the MPHG on aconveyorized belt that could be operated at a variable speed to controlthe cure time.

In the following examples, adhesion of the cured ink was determined byboiling the printed substrate in water for two minutes, rubbing the inkwith a finger, and observing the amount of ink thereby removed.

The cure of the ink is defined herein as the conversion of afree-flowing liquid to a tack-free solid that forms a film that cannotbe scratched by a fingernail.

Flexibility of the cured ink in the following examples was determined byboiling a printed substrate for two minutes and stretching the casing toits maximum elongation and observing whether cracking of the ink filmoccurred.

EXAMPLE 1

Five ink compositions were formulated as indicated in Table B. Thenumbers in Table B refer to the amount of the indicated components inthe ink composition in weight percent of the total ink composition. Thepigment used was Napthol Red F5RK, available from American Hoechst, Dyes& Pigment Division, Coventry, R. I. The reactive diluent used wasN-vinyl-2-pyrrolidone, available from GAF Corporation, New York, NewYork under the name "V-Pyrol™". The photoinitiator used was2,2-dimethoxy-2-phenylacetophenone, available from Ciba-GeigyCorporation, Ardsley, New York under the name "Irgacure 651™".

                  TABLE B                                                         ______________________________________                                        Formulation                                                                              A         B     C       D   E                                      ______________________________________                                        PU-B       70        --    35      50  20                                     APU-C      --        70    35      20  50                                     Pigment    15        15    15      15  15                                     Reactive Diluent                                                                         10        10    10      10  10                                     Photoinitiator                                                                            5         5     5       5   5                                     ______________________________________                                    

The inks were made and applied as described above to a fibrousreinforced cellulosic casing. Before application of the ink, the casingwas primed with a primer coat comprising 19.2 weight percent of anacrylic ester, 76.9 weight percent 2-Nitropropane, and 3.9 weightpercent of a polyfunctional isocyanate prepared by reacting 1 mole oftrimethylol propane with 4.2 moles of propylene oxides. The isocyanatewas obtained as "Desmodur N™" from Mobay Chemical Corporation,Pittsburgh, Pa. The inks were then cured by passing the casing substratewith the uncured ink applied thereon through the above described curingapparatus at a speed of about 200 ft/min (1.02 m/s).

After the cure, each formulation was evaluated for flexibility by theabove described method and the surface was observed for the extent ofcure. The results are summarized in Table C.

                  TABLE C                                                         ______________________________________                                        Formulation Flexibility     Cure                                              ______________________________________                                        A           Brittle         Hard, Glossy,                                                                 Fully Cured                                       B           Good            Soft, Tacky,                                                                  Uncured                                           C           Good            Glossy,                                                                       Fully Cured                                       D           Marginal        Fully Cured                                       E           --              Soft, Tacky,                                                                  Uncured                                           ______________________________________                                    

As shown by the data shown in Table C, formulations A and D, whichcontain no or an inadequate proportion of the second urethane of theinvention (an acrylate capped polycaprolactone) have excellent curingproperties but have unacceptable or only marginal flexibilityproperties. Formulation B, having no or an inadequate proportion of theirst urethane of the invention (a polyol urethane), has good flexibilityproperties but does not cure in the rapid cure conditions of thisexample to form a fully cured impression. Likewise, formulation E, whichhas an inadequate amount of the first urethane, does not adequatelycure. Formulation C, which illustrates the present invention, shows bothgood curing and flexibility properties.

EXAMPLE 2

Four additional ink formulations were prepared using the procedure ofExample 1. The pigment was 2B-Red. The photo initiator was isobutylbenzoin ether, available from Stauffer Chemical Company, Westport,Connecticut, under the name "Vicure 10™". The components and the amountof each component in weight percent in each formulation are shown inTable D.

                  TABLE D                                                         ______________________________________                                        Formulation       A      B                                                    ______________________________________                                        PU-B              31.8   77.3                                                 APU-C             45.5   --                                                   Vicure 10          9.1    9.1                                                 Pigment           13.6   13.6                                                 ______________________________________                                    

The ink formulations were applied as in Example 1 to a cellulosic casingsubstrate primed with the primer of Example 1 and cured as in Example 1except that the speed of the conveyor was set at 400 ft/min (2.03 m/s).The inks were evaluated as described above for adhesion, flexibility andextent of cure. The results are summarized in Table E.

                  TABLE E                                                         ______________________________________                                        Formulation                                                                              Adhesion     Flexibility                                                                             Cure                                        ______________________________________                                        A          Good         Good      Cured                                       B          Good         Poor      Cured                                       ______________________________________                                    

As shown by the data shown in Table E, formulation A which was madeaccording to the invention has good adhesion, flexibility, and cureproperties, whereas formulation B, which is not within the scope of theinvention, has poor flexibility.

EXAMPLE 3

Various pigments and reactive diluent monomers were used in inkformulations made according to the invention and their effect on curerate was evaluated.

Formulations containing different ultraviolet light photoinitiators weremade and evaluated for cure speed. The inks were made, applied to apolyethylene film substrate, and cured as described above. Threedifferent pigments were used; a titanium dioxide pigment (white), HRYellow pigment (yellow), and Napthol Red. The first urethane used isshown in Tables G, I and K. The second urethane used was APU-A. Thereactive diluent monomer used was the same as that used in Example 1.The ultraviolet photoinitiators (UVP) used were isobutyl benzoin ether(IBE), obtained from Stauffer Chemical Company, Westport, Conn., underthe name "Vicure 10™", 2,2-dimethoxy-2-phenyl- acetophenone (DMP),obtained from Ciba-Geigy Corporation, Ardsley, New York, under the name"Irgacure 651™", benzoin methyl ether (BME), diethoxy acetophenone(DEAP), and a 20 wt. % solution of Michler's Ketone in benzophenone(MK). In Tables F, M, and J are shown, in weight percent of the totalcomposition, the amounts of the components used in the formulations foreach pigment tested. In Tables G, I, and K are shown the cure speeds forthe inks of Tables F, H and J, respectively, using different ultravioletinitiators. "Cure speed" is the maximum speed of the conveyor of thephotocure system at which the ink is cured. The cure speeds are shown inthe format, XXX(Y.YY), where XXX is the speed in feet per minute andY.YY is the speed in meters per second. The highest conveyor speed usedin the tests of this example was 275 ft/sec (1.40 m/s). The cure speedsof the compositions of Table H would have been higher if a higherconveyor speed could have been used, indicating a more rapid cure rate.The asterisk by a speed denotes that the composition was not cured atthat speed.

                  TABLE F                                                         ______________________________________                                        White                                                                         Component        Wt. %                                                        ______________________________________                                        Pigment          30.0                                                         First Urethane   30.0                                                         Second Urethane  35.0                                                         Photo Initiator  5.0                                                          ______________________________________                                    

                  TABLE G                                                         ______________________________________                                        Cure Speed - White                                                                   First Urethane                                                         UVP      AEDOU-A       PU-B     PU-A                                          ______________________________________                                        IBE       115(0.58)*   200(1.02)                                                                              175(0.89)                                     DMP      200(1.02)     275(1.40)                                                                              250(1.27)                                     BME      115(0.58)     --       200(1.02)                                     DEAP     115(0.58)     --       115(0.58)                                     MK       115(0.58)     200(1.02)                                                                              115(0.58)                                     ______________________________________                                    

                  TABLE H                                                         ______________________________________                                        Yellow                                                                        Component        Wt. %                                                        ______________________________________                                        Pigment          14.2                                                         First Urethane   33.3                                                         Second Urethane  38.0                                                         Reactive Diluent 9.5                                                          Photo Initiator  5.0                                                          ______________________________________                                    

                  TABLE I                                                         ______________________________________                                        Cure Speed - Yellow                                                                       First Urethane                                                    UVP           AEDOU-A   PU-B                                                  ______________________________________                                        IBE           275(1.40) 275(1.40)                                             DMP           275(1.40) 275(1.40)                                             BME           275(1.40) 275(1.40)                                             DEAP          275(1.40) 275(1.40)                                             TR            275(1.40) 275(1.40)                                             ______________________________________                                    

                  TABLE J                                                         ______________________________________                                        Red                                                                           Component        Wt. %                                                        ______________________________________                                        Pigment          14.2                                                         First Urethane   33.3                                                         Second Urethane  38.0                                                         Reactive Diluent 9.5                                                          Photo Initiator  5.0                                                          ______________________________________                                    

                  TABLE K                                                         ______________________________________                                        Cure Speed - Red                                                                          First Urethane                                                    UVP           AEDOU-A   PU-B                                                  ______________________________________                                        IBE           115(0.58) 275(1.40)                                             BME           275(1.40) 275(1.40)                                             DMP           200(1.02) 275(1.40)                                             ______________________________________                                    

The results shown above demonstrate the practice of the invention andthe rapid curing rates obtainable thereby.

EXAMPLE 4

Ink compositions of the invention and ink compositions containing otheracrylated-typed urethanes were made and evaluated. The components in theink composition of the invention and the amounts thereof, in weightpercent of the total composition, are shown in Table L. Other inkcompositions were made as the composition of the invention except otheracrylated-type urethane was used in place of APU-C. The acrylated-typeurethanes used were polyol urethanes available as "Uvithane™" 782, 783,and 788, from Polychrome Corporation. Yonkers, New York anddifunctional, hydroxyl terminated urethane resins available as"Purelast™" 166, 169, 176, and 186, from Polymer Systems Corp., LittleFalls, N.J. The pigment was titanium dioxide "R-915™" identified inExample 3, and the reactive diluent and the photoinitiator were the sameas in Example 3.

                  TABLE L                                                         ______________________________________                                        Ink Composition                                                               Component        Wt. %                                                        ______________________________________                                        Pigment          28.5                                                         APU-C            33.2                                                         PU-B             28.5                                                         Reactive Diluent 4.8                                                          Photoinitiator   5.0                                                          ______________________________________                                    

Uvithane 782, 783, 788 resulted in flexible coatings but the cure ratewas very slow. The viscosity was also very high causing difficulty inhandling. Purelast 166, 169, 176 , 186 produced brittle ink impressionswith only moderate to poor cure rates. Uvithane 893 produced a flexiblefilm with a good cure rate, but the viscosity was too high, resulting indifficulty in handling.

The results here show the difficulty in obtaining a suitable inkcomposition for use on sausage casings and the like. As described above,the inks produced either were too viscous, too brittle or had inadequatecure rates. It is therefore, unexpected that a ultraviolet light curableink that has the advantageous properties of the invention, rapid curerate, high flexibility and low viscosity, could be produced.

Tests were also made from a first urethane and plasticizers commonlyused in the art, in an attempt to provide for more flexibility. It wasfound that the plasticizer containing inks were more flexible than thebrittle inks containing only a first urethane. However, the cure-ratewas adversely affected such that these formulations were unsuitable. Bypractice of the invention, using the first urethane and the secondurethane as defined, herein, it was possible to make low viscosity,rapidly curable inks that formed flexible adhering impressions suitablefor flexible films.

EXAMPLE 5

Three ink formulations were made and evaluated. The components and theamounts thereof, in weight percent of the total compositions are inTables M, N and O. The reactive diluent was glycidyl methacrylate (GMA),obtained from Blemmer Chemical, West Caldwell, New Jersey, under thename "Blemmer G™". The white pigment was titanium dioxide "R-915™"described in Example 3; the yellow pigments were AAOA-Yellow, and H.R.Yellow, and the red pigment was Naphthol Red. The photoinitiator was amixture of benzophenone and Michler's Ketone. An organic derivative of aspecial magnesium montmonillonite, available as "Bentone 38™" from NLChemicals, Heighstown, N.J., was used as a rheological agent.

                  TABLE M                                                         ______________________________________                                        Component        Wt. %                                                        ______________________________________                                        Titanium Dioxide 29.1                                                         PU-B             36.9                                                         APU-B            31.0                                                         Michler's Ketone 3.0                                                          ______________________________________                                    

                  TABLE N                                                         ______________________________________                                        Component        Wt. %                                                        ______________________________________                                        Titanium Dioxide 21.2                                                         AAOA Yellow      2.7                                                          H.R. Yellow      2.1                                                          PU-B             33.6                                                         APU-B            24.4                                                         GMA              4.4                                                          Benzophenone     7.0                                                          Michler's Ketone 3.0                                                          Bentone 38       1.5                                                          ______________________________________                                    

                  TABLE O                                                         ______________________________________                                        Component        Wt. %                                                        ______________________________________                                        Naphthol Red     10.6                                                         PU-B             35.4                                                         APU-B            35.4                                                         GMA              7.1                                                          Benzonephenone   7.0                                                          Michler's Ketone 3.0                                                          Bentone 38       1.5                                                          ______________________________________                                    

The inks were made as described above. The inks were applied to an MPfibrous casing substrate using a letter press. Each of the three inks,above, were applied individually in layers on the substrate to form amulticolored pattern. After delivery from the press, and afterapplication of the third ink layer, the substrates were conveyed on abelt at a speed of 160 feet/minute (0.81 m/s) through the MPHGphotocuring unit, described above, with no inerting in the photocuringunit. The colors printed over uncured or partially cured ink were foundto have good intercoat adhesion. When the ink was applied over a fullycured ink, the intercoat adhesion was poor.

Samples of the above printed casing were boiled for about 5 to 10minutes in a solution having a pH of about 9 to 10. The samples weretested for adhesion and scuff resistance. A conventional oleoresinousink commonly used in letter-press printing on flexible films was alsoapplied to an MP fibrous casing and tested in the same manner. Theprinted impressions of each sample were rubbed and scuffed by a finger.The ink made according to the present invention was not removed, whilethe conventional ink was rubbed off.

What is claimed:
 1. An ultraviolet light curable ink composition whichcomprises;(i) a first urethane comprising a polyol urethane which is thereaction product of about one equivalent of an isocyanate containingintermediate, the isocyanate intermediate being the reaction product ofabout one equivalent of a monomeric diol and about two equivalents of anorganic polyisocyanate, and about one equivalent oF a monomericolefinically unsaturated compound containing exactly one activehydrogen, and (ii) a second urethane comprising an acrylate-cappedpolycaprolactone which is the reaction product of a caprolactone polyol,a substituted or unsubstituted isocyanate, and an acrylyl compound, anddefined by the formula; ##STR9## where Z is hydrogen or methyl; Q is theresidue of the caprolactone polyol, R is a linear or branched divalentalkylene having from 2 to about 5 carbon atoms; G is a linear orbranched alkylene having from 1 to about 10 carbon atoms, or arylene,alkarylene and aralkylene having from 6 to about 12 carbon atoms,cycloalkylene having from 5 to about 10 carbon atoms, or bicycloalkylenehaving from 7 to about 15 carbon atoms; and x is an integer having avalue from 1 to 4; (iii) an ultraviolet photoinitiator in an amountsufficient to cure the ink composition when exposed to ultravioletlight, and (iv) a pigment; wherein the first urethane and the secondurethane are present in an amount such that the weight ratio of thefirst urethane to the second urethane is from about 2:5 to about 3:2. 2.The composition of claim 1 wherein the weight ratio of the firsturethane to the second urethane is from about 3:5 and about 5:5.
 3. Thecomposition of claim 1 comprising additionally a reactive diluentmonomer.
 4. The composition of claim 3 wherein the reactive diluentmonomer is glycidyl methacrylate or N-vinyl-2-pyrrolidone.
 5. Thecomposition of claim 1 wherein the monomeric olefinically unsaturatedcompound in (i) is an acrylate or methacrylate.
 6. The composition ofclaim 1 wherein the monomeric olefinically unsaturated compound isacrylic acid, cinnamic acid, methacrylic acid, a hydroxyalkyl acrylate,a hydroxyalkyl methacrylate, cinnamyl alcohol, allyl alcohol, diacetoneacrylamide or an unsaturated compound containing secondary amino oramido groups.
 7. the composition of claim 1 wherein the polyisocyanatein (i) is a diisocyanate.
 8. The composition of claim 1 wherein thepolyol in (i) is a triol.
 9. the composition of claim 1 wherein Z ismethyl.
 10. The composition of claim 1 wherein Z is hydrogen.
 11. Thecomposition of claim 1 wherein x is
 2. 12. The composition of claim 1wherein G is the polyvalent residue remaining after reaction ofisophorone diisocyanate with the caprolactone polyol and acrylylcompound.
 13. The composition of claim 1 wherein G is the polyvalentresidue remaining after reaction of tetramethylene diisocyanate with thecaprolactone polyol and acrylyl compound.
 14. The composition of claim 1wherein R is a linear alkylene having 2 or 3 carbon atoms.
 15. Thecomposition of claim 1 wherein the caprolactone polyol is the reactionproduct of a caprolactone having the structure; ##STR10## and adihydroxyl compound.
 16. The composition of claim 15 wherein thedihydroxyl compound is ethylene glycol or diethylene glycol.
 17. Thecomposition of claim 15 wherein the caprolactone isepsilon-caprolactone.
 18. The composition of claim 1 wherein thecombined amounts of the first urethane and the second urethane are fromabout 20 to about 80 weight percent, the photoinitiator is present in anamount from about 1 to about 10 weight percent, and the pigment ispresent in an amount greater than 0 to about 70 weight percent, based onthe total weight of the composition.
 19. The composition of claim 1wherein the combined amounts of the first urethane and the secondurethane are from about 50 to about 70 weight percent, thephotoinitiator is present in an amount rom about 3 to about 7 weightpercent, and the pigment is present in an amount from about 10 to about50 weight percent, based on the total weight of the composition.
 20. Thecomposition of claim 18 wherein a reactive diluent is present in anamount from about 2 to about 30 weight percent, based on the totalweight of the composition.
 21. The composition of claim 19 wherein areactive diluent is present in an amount from about 5 to about 20 weightpercent, based on the total weight of the composition.
 22. A process forthe application of ink impressions upon a substrate comprising;providing an ultraviolet curable ink as defined in claim 1, applying theultraviolet curable ink composition upon a substrate to form a printedimpression upon the substrate, and exposing the printed impression uponthe substrate to cure said impression to tack-free state.
 23. A curedink film upon a substrate which comprises the reaction product of anultraviolet light curable ink which comprises;(i) a first urethanecomprising a polyol urethane which is the reaction product of about oneequivalent of an isocyanate containing intermediate, the isocyanateintermediate being the reaction product of about one equivalent of amonomeric diol and about two equivalents of an organic polyisocyanate,and about one equivalent of a monomeric olefinically unsaturatedcompound containing exactly one active hydrogen, and (ii) a secondurethane comprising an acrylate-capped polycaprolactone which is thereaction product of a caprolactone polyol, a substituted orunsubstituted isocyanate, and a acrylyl compound, and defined by theformula; ##STR11## where Z is hydrogen or methyl; Q is the residue ofthe caprolactone polyol, R is the linear or branched divalent alkylenehaving from 2 to about 5 carbon atoms; G is a linear or branchedalkylene having from 1 to 10 carbon atoms, or arylene, alkarylene andaralkylene having from 6 to about 12 carbon atoms, cycloalkylene havingfrom 5 to about 10 carbon atoms, or bicycloalkylene having from 7 toabout 15 carbon atoms; and x is an integer having a value from 1 to 4;(iii) an ultraviolet photoinitiator in the amount sufficient to cure theink composition when exposed to ultraviolet light, and (v) apigment;wherein the first urethane and the second urethane are presentin an amount such that the weight ratio of the first urethane to thesecond urethane is from about 2:5 to about 3:2.
 24. The film of claim 23wherein the weight ratio of the first urethane to the second urethane isfrom about 3:5 about about 5:5.
 25. The film of claim 23 comprisingadditionally a reactive diluent monomer.
 26. The film of claim 25wherein the reactive diluent monomer is glycidyl methacrylate orN-vinyl-2-pyrrolidone.
 27. The film of claim 23 wherein the monomericolefinically unsaturated compound in (i) is an acrylate or methacrylate.28. The film of claim 23 wherein the monomeric olefinically unsaturatedcompound is acrylic acid, cinnamic acid, methacrylic acid, ahydroxyalkyl acrylate, a hydroxyalkyl methacrylate, cinnamyl alcohol,allyl alcohol, diacetone acrylamide or an unsaturated compoundcontaining secondary amino or amido groups.
 29. The film of claim 23wherein the polyisocyanate in (i) is a diisocyanate.
 30. The film ofclaim 23 wherein the polyol in (i) is a triol.
 31. The film of claim 23wherein Z is methyl.
 32. The film of claim 23 wherein Z is hydrogen. 33.The film of claim 23 wherein x is
 2. 34. The film of claim 23 wherein Gis the polyvalent residue remaining after reaction of isophoronediisocyanate with the caprolactone polyol and acrylyl compound.
 35. Thefilm of claim 23 wherein G is the polyvalent residue remaining afterreaction of tetramethylene diisocyanate with the caprolactone polyol andacrylyl compound.
 36. The film of claim 23 wherein R is a linearalkylene having 2 or 3 carbon atoms.
 37. The film of claim 23 whereinthe caprolactone polyol is the reaction product of a caprolactone havingthe structure ##STR12## and a dihydroxyl compound.
 38. The film of claim37 wherein the dihydroxyl compound is ethylene glycol or diethyleneglycol.
 39. The film of claim 37 wherein the caprolactone isepsilon-caprolactone.
 40. The film of claim 23 wherein the substratecomprises regenerated cellulose, polyethylene, ethylene vinyl acetate,polyvinylidene chloride, or polyvinyl chloride.
 41. The film of claim 40wherein the film comprises regenerated cellulose.
 42. The film of claim40 wherein the substrate is a sausage casing.
 43. An ultraviolet lightcurable ink which comprises:(i) a first urethane which comprises thereaction product of an acrylated expoxidized drying oil and and organicisocyanate, and (ii) a second urethane comprising an acrylate-cappedpolycaprolactone which is the reaction product of a caprolactone polyol,a substituted or unsubstituted isocyanate, and a acrylyl compound, anddefined by the formula: ##STR13## where Z is hydrogen or methyl; Q isthe residue of the caprolactone polyol, R is a linear or brancheddivalent alkylene having from 2 to about 5 carbon atoms; G is a linearor branched alkylene having from 1 to about 10 carbon atoms, or arylene,alkarylene and aralkylene having from 6 to about 12 carbon atoms,cycloalkylene having from 5 to about 10 carbon atoms, or bicycloalkylenehaving 7 to about 15 carbon atoms; and x is an integer having a valuefrom 1 to 4; (iii) an ultraviolet photoinitiator in an amount sufficientto cure the ink composition when exposed to ultraviolet light, and (iv)a pigment;wherein the first urethane and the second urethane are presentin an amount such as that the weight ratio of the first urethane to thesecond urethane is from about 2:5 to about 3:2.
 44. The composition ofclaim 43 wherein the first urethane comprises an acrylated epoxidizeddrying-oil urethane having in the molecule the group: ##STR14## whereinX is hydrogen or methyl, the acrylated epoxidized drying-oil urethanebeing the reaction product of epoxidized drying-oil reacted with acrylicor methacrylic and an organic isocyanate.
 45. The composition of claim43 wherein the acrylated epoxidized drying oil is the reaction productof epoxidized soybean oil and pentaerythritrol acrylate.
 46. Thecomposition of claim 45 wherein the pentaerthritrol acrylate has anaverage functionality of between about 3.1 and about 3.3.